Atherosclerotic occlusions in coronary and peripheral circulations are commonly treated with angioplasty/stinting or vein bypass graft surgery. These interventions can fail over time due to intimal hyperplasia, an exaggerated healing response in the vessel wall that leads to narrowing and occlusion. The lesion consists of vascular smooth muscle cells (VSMC) with a proliferative and de-differentiated phenotype. Understanding the molecular pathways which regulate this injury response is critical for the development of new therapeutics. Survivin (SVV) is a novel protein that regulates both apoptosis and proliferation. Therefore I hypothesize that SVV has a crucial role in controlling VSMC phenotype. I hypothesize that SVV expression in activated VSMC is constitutively elevated in a deregulated fashion. The primary goal of this translational research project is to validate SVV as a therapeutic target in intimal hyperplasia. My first aim is to characterize the effects of SVV gene targeting on cell cycle progression in VSMC. Proliferation assays will be performed on VSMC transuded with SVV knockdown and flow cytometry will be used to quantitative the fraction of cells in each phase of the cell cycle. I hypothesize that SVV knockdown will be cytostatic in VSMC and will blunt the proliferative response to exogenous growth factors such as platelet-derived growth factor (PDGF). My second aim is to examine the effects of SVV gene knockdown on growth factor signaling pathways in VSMC. VSMC transuded with SVV knockdown will be exposed to agonists and the expression of various growth factors will be examined by quantitative RT-PCR, Western blot, and ELISA of conditioned media. I hypothesize that SVV knockdown will reduce autocrine/paracrine signaling in VSMC, specifically the PDGF pathway, which is of established relevance to intimal hyperplasia. My third aim is to determine the effects of locally targeted SVV gene inhibition in a mouse model of arterial injury. siRNA targeting SVV will be delivered to the artery locally, which will then be examined at various time points for changes in proliferation and apoptosis by immunostaining and morphometric analysis. I hypothesize that treated vessels will exhibit reduced VSMC proliferation, increased apoptosis, and a resulting reduction in neointimal formation in-vivo. PUBLIC HEALTH RELEVANCE: Atherosclerotic occlusions in the coronary and peripheral circulation are currently treated with angioplasty, stenting, or vein bypass graft surgery. However, these interventions fail over time due to intimal hyperplasia in the vessel wall that leads to reocclusion. Understanding the role of survivin, a novel protein that regulates apoptosis and proliferation, in the development of intimal hyperplasia is critical for the development of new therapeutics to treat this disease of major public health magnitude.